Children usually enjoy practising placing his toys or belongings in order by size. First you need to teach them the comparison – introduce them the concept of Big / Large and Small before heading to the following activity.
There are many free printable on line regarding size sequence for preschoolers. If you don’t have a printer for those colorful printable, you may try the following activity. Any toys or belongings or even food can used for this size sequence activities.
You may also teach your children to arrange their toys in order by size. This is one of the way I invite my son to sort his favourite car and Legos, surprisingly he can understand what is big and what is small and sort out correctly.
Try it out. Then u can teach him other comparison, i.e. more vs less, tall Vs short, long Vs short etc. Good luck.